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The Respiratory System What are the primary functions of the respiratory system? Oxygen • Is obtained from the air by diffusion across delicate exchange surfaces of lungs • Is carried to cells by the cardiovascular system which also returns carbon dioxide to the lungs 5 Functions of the Respiratory System 1. Provides extensive gas exchange surface area between air and circulating blood 2. Moves air to and from exchange surfaces of lungs 5 Functions of the Respiratory System 3. Protects respiratory surfaces from outside environment 4. Produces sounds-speaking, singing 5. Participates in olfactory sense Components of the Respiratory System Figure 23–1 Organization of the Respiratory System • The respiratory system is divided into the upper respiratory system, above the larynx, and the lower respiratory system, from the larynx down The Respiratory Tract • Consists of a conducting portion: – from nasal cavity to terminal bronchioles • Consists of a respiratory portion: – the respiratory bronchioles and alveoli Are air-filled pockets within the lungs • where all gas exchange takes place The Respiratory Epithelium Figure 23–2 Alveolar sac Alveoli Figure 23–2 The Respiratory Epithelium • For gases to exchange efficiently: – alveoli walls must be very thin (< 1 µm) – surface area must be very great (about 35 times the surface area of the body) The Respiratory Mucosa • Consists of: – an epithelial layer – an areolar layer • Lines conducting portion of respiratory system The Lamina Propria • Underlies areolar tissue • In the upper respiratory system, trachea, and bronchi: – contains mucous glands that secrete onto epithelial surface • In the conducting portion of lower respiratory system: – contains smooth muscle cells that encircle lumen of bronchioles How are delicate respiratory exchange surfaces protected from pathogens, debris, and other hazards? The Respiratory Defense System • Consists of a series of filtration mechanisms • Removes particles and pathogens Components of the Respiratory Defense System (1 of 2) • Goblet cells and mucous glands: – produce mucus that bathes exposed surfaces • Cilia: – sweep debris trapped in mucus toward the pharynx (mucus escalator) Components of the Respiratory Defense System (2 of 2) • Filtration in nasal cavity removes large particles • Alveolar macrophages engulf small particles that reach lungs What are the organs of the upper respiratory system and their functions? The Upper Respiratory System Figure 23–3 The Nose • Air enters the respiratory system: – through nostrils or external nares – into nasal vestibule • Nasal hairs: – are in nasal vestibule – are the first particle filtration system The Nasal Cavity • The nasal septum: – divides nasal cavity into left and right • Mucous secretions from paranasal sinus and tears: – clean and moisten the nasal cavity • Superior portion of nasal cavity is the olfactory region: – provides sense of smell • From vestibule to internal nares: – through superior, middle, and inferior meatuses Air Flow Meatuses • Constricted passageways that produce air turbulence: – warm and humidify incoming air – trap particles The Palates • Hard palate: – forms floor of nasal cavity – separates nasal and oral cavities • Soft palate: – extends posterior to hard palate – divides superior nasopharynx from lower pharynx The Nasal Mucosa • Warm and humidify inhaled air for arrival at lower respiratory organs • Breathing through mouth bypasses this important step The Pharynx • A chamber shared by digestive and respiratory systems • Extends from internal nares to entrances to larynx and esophagus Divisions of the Pharynx • Nasopharynx • Oropharynx • Laryngopharynx The Nasopharynx • Superior portion of the pharynx • Contains pharyngeal tonsils and openings to left and right auditory tubes The Oropharynx • Middle portion of the pharynx • Communicates with oral cavity The Laryngopharynx • Inferior portion of the pharynx • Extends from hyoid bone to entrance to larynx and esophagus What is the structure of the larynx and its role in normal breathing and production of sound? Anatomy of the Larynx Figure 23–4 Cartilages of the Larynx • 3 large, unpaired cartilages form the larynx: – the thyroid cartilage – the cricoid cartilage – the epiglottis The Thyroid Cartilage • Also called the Adam’s apple • Is a hyaline cartilage • Forms anterior and lateral walls of larynx • Ligaments attach to hyoid bone, epiglottis, and laryngeal cartilages The Cricoid Cartilage • Is a hyaline cartilage • Form posterior portion of larynx • Ligaments attach to first tracheal cartilage • Articulates with arytenoid cartilages The Epiglottis • Composed of elastic cartilage • Ligaments attach to thyroid cartilage and hyoid bone Cartilage Functions • Prevents entry of food and liquids into respiratory tract – During swallowing: – the larynx is elevated – the epiglottis folds back over glottis • Thyroid and cricoid cartilages support and protect: – the glottis – the entrance to trachea The Glottis Figure 23–5 Sound Production • Air passing through glottis: – vibrates vocal folds – produces sound waves Sound Variation • Sound is varied by: – tension on vocal folds – voluntary muscles (position arytenoid cartilage relative to thyroid cartilage) Speech • Is produced by: – phonation: • sound production at the larynx – articulation: • modification of sound by other structures What is the structure of airways outside the lungs? Anatomy of the Trachea Figure 23–6 The Trachea • Also called the windpipe • Extends from the cricoid cartilage into mediastinum – where it branches into right and left pulmonary bronchi The Tracheal Cartilages • 15–20 tracheal cartilages: – strengthen and protect airway – discontinuous where trachea contacts esophagus • Ends of each tracheal cartilage are connected by: – an elastic ligament and trachealis muscle The Primary Bronchi • Right and left primary bronchi: – separated by an internal ridge (the carina) The Right Primary Bronchus • Is larger in diameter than the left • Descends at a steeper angle Structure of Primary Bronchi • Each primary bronchus: – travels to a groove (hilus) along medial surface of the lung Hilus • Where pulmonary nerves, blood vessels, and lymphatics enter lung • Anchored in meshwork of connective tissue What are the superficial anatomy of the lungs, the structure of a pulmonary lobule, and the functional anatomy of the alveoli? Gross Anatomy of the Lungs Figure 23–7 The Lungs • Left and right lungs: – are in left and right pleural cavities • The base: – inferior portion of each lung rests on superior surface of diaphragm The Right Lung • Has 3 lobes: – superior, middle, and inferior – separated by horizontal and oblique fissures The Left Lung • Has 2 lobes: – superior and inferior – are separated by an oblique fissure Relationship between Lungs and Heart Figure 23–8 Lung Shape • Right lung: – is wider – is displaced upward by liver • Left lung: – is longer – is displaced leftward by the heart forming the cardiac notch The Bronchial Tree • Is formed by the primary bronchi and their branches Extrapulmonary Bronchi • The left and right bronchi branches outside the lungs Intrapulmonary Bronchi • Branches within the lungs A Primary Bronchus • Branches to form secondary bronchi (lobar bronchi) • 1 secondary bronchus goes to each lobe Bronchi and Lobules Figure 23–9 Secondary Bronchi • Branch to form tertiary bronchi, also called the segmental bronchi • Each segmental bronchus: – supplies air to a single bronchopulmonary segment Bronchial Structure • The walls of primary, secondary, and tertiary bronchi: – contain progressively less cartilage and more smooth muscle – increasing muscular effects on airway constriction and resistance Bronchitis • Inflammation of bronchial walls: – causes constriction and breathing difficulty The Bronchioles Figure 23–10 Bronchiole Structure • Bronchioles: – have no cartilage – are dominated by smooth muscle Autonomic Control • Regulates smooth muscle: – controls diameter of bronchioles – controls airflow and resistance in lungs Bronchodilation • Dilation of bronchial airways • Caused by sympathetic ANS activation • Reduces resistance Bronchoconstriction • Constricts bronchi • Caused by: – parasympathetic ANS activation – histamine release (allergic reactions) Asthma • Excessive stimulation and bronchoconstriction • Stimulation severely restricts airflow Trabeculae • Fibrous connective tissue partitions from root of lung • Contain supportive tissues and lymphatic vessels • Branch repeatedly • Divide lobes into increasingly smaller compartments Pulmonary Lobules • Are the smallest compartments of the lung • Are divided by the smallest trabecular partitions (interlobular septa) Surfaces of the Lungs • Each terminal bronchiole delivers air to a single pulmonary lobule • Each pulmonary lobule is supplied by pulmonary arteries and veins Exchange Surfaces • Within the lobule: – each terminal bronchiole branches to form several respiratory bronchioles, where gas exchange takes place The Bronchioles • Each tertiary bronchus branches into multiple bronchioles • Bronchioles branch into terminal bronchioles: – 1 tertiary bronchus forms about 6500 terminal bronchioles Alveolar Organization Figure 23–11 Alveolar Organization • Respiratory bronchioles are connected to alveoli along alveolar ducts • Alveolar ducts end at alveolar sacs: – common chambers connected to many individual alveoli An Alveolus • Has an extensive network of capillaries • Is surrounded by elastic fibers Alveolar Epithelium • Consists of simple squamous epithelium • Consists of thin, delicate Type I cells • Patrolled by alveolar macrophages, also called dust cells • Contains septal cells (Type II cells) that produce surfactant Surfactant • Is an oily secretion • Contains phospholipids and proteins • Coats alveolar surfaces and reduces surface tension Respiratory Membrane • The thin membrane of alveoli where gas exchange takes place 3 Parts of the Respiratory Membrane 1. Squamous epithelial lining of alveolus 2. Endothelial cells lining an adjacent capillary 3. Fused basal laminae between alveolar and endothelial cells Inflammation of Lobules • Also called pneumonia: – causes fluid to leak into alveoli – compromises function of respiratory membrane Pleural Cavities and Pleural Membranes Figure 23–8 Pleural Cavities and Pleural Membranes • 2 pleural cavities: – are separated by the mediastinum • Each pleural cavity: – holds a lung – is lined with a serous membrane (the pleura) The Pleura • Consists of 2 layers: – parietal pleura – visceral pleura • Pleural fluid: – lubricates space between 2 layers Respiration • Refers to 2 integrated processes: – external respiration – internal respiration External Respiration • Includes all processes involved in exchanging O2 and CO2 with the environment Internal Respiration • Also called cellular respiration • Involves the uptake of O2 and production of CO2 within individual cells 3 Processes of External Respiration 1. Pulmonary ventilation (breathing) 2. Gas diffusion: – across membranes and capillaries 3. Transport of O2 and CO2: – – between alveolar capillaries between capillary beds in other tissues What physical principles govern the movement of air into the lungs? Pulmonary Ventilation • Is the physical movement of air in and out of respiratory tract • Provides alveolar ventilation Gas Pressure and Volume Figure 23–13 Atmospheric Pressure • The weight of air: – has several important physiological effects Boyle’s Law • Defines the relationship between gas pressure and volume: • As volume decreases, pressure increases • In a contained gas: – external pressure forces molecules closer together – movement of gas molecules exerts pressure on container Mechanisms of Pulmonary Ventilation Figure 23–14 Respiration • Causes volume changes that create changes in pressure • Volume of thoracic cavity changes: – with expansion or contraction of diaphragm or rib cage The Respiratory Muscles Figure 23–16a, b The Respiratory Muscles Figure 23–16c, d 3 Muscle Groups of Inhalation 1. Diaphragm: – – contraction draws air into lungs 75% of normal air movement 2. External intracostal muscles: – – assist inhalation 25% of normal air movement 3. Accessory muscles assist in elevating ribs: – – – – sternocleidomastoid serratus anterior pectoralis minor scalene muscles Changes in Respiratory System at Birth (1 of 5) 1. Before birth: – – pulmonary vessels are collapsed lungs contain no air 2. During delivery: – placental connection is lost – blood PO falls – PCO rises 2 2 3. At birth: – newborn overcomes force of surface tension to inflate bronchial tree and alveoli and take first breath Changes in Respiratory System at Birth (4 of 5) 4. Large drop in pressure at first breath: – – – pulls blood into pulmonary circulation closing foramen ovale and ductus arteriosus redirecting fetal blood circulation patterns 5. Subsequent breaths: – fully inflate alveoli Respiratory Performance and Age Figure 23–28 3 Effects of Aging on the Respiratory System 1. Elastic tissues deteriorate: – – reducing lung compliance lowering vital capacity 2. Arthritic changes: – – restrict chest movements limit respiratory minute volume 3. Emphysema: – – affects individuals over age 50 depending on exposure to respiratory irritants (e.g., cigarette smoke)